Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch sensitive devices, such as touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. A touch sensitive device can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. The touch sensitive device can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location dictated by a user interface (UI) being displayed by the display device. In general, the touch sensitive device can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.
When either the object touching at the touch sensor panel or the touch sensitive device itself is poorly grounded, touch output values can be erroneous or otherwise distorted. More specifically, various capacitances, such as the object's body capacitance between the object, e.g., a finger, and ground can distort the capacitances measured at the touch sensor panel, which can be utilized to generate the touch output values. The possibility of such erroneous or distorted values can further increase when two or more simultaneous touch events occur at the touch sensor panel.